insight-chat: code-review polish on the tool-gating PR

- search_messages now delegates to search_messages_with_contact(.., None)
  so the two methods share a single HTTP path. Drops the dead-code
  warning and the ~30-line duplication.
- DailySummaryDao gains has_any_summaries (LIMIT 1 existence probe)
  used by current_gate_opts; the SELECT COUNT(*) get_total_summary_count
  added in the prior commit is removed (it had no other caller).
- current_gate_opts doc comment corrected to describe what the probes
  actually do.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ai/sms_client.rs

@@ -261,38 +261,16 @@ impl SmsApiClient {
     ///   - "fts5"     keyword-only, supports phrase / prefix / boolean / NEAR
     ///   - "semantic" embedding similarity
     ///   - "hybrid"   both merged via reciprocal rank fusion (recommended)
+    ///
+    /// Equivalent to `search_messages_with_contact(query, mode, limit, None)`;
+    /// kept as a convenience for callers that don't filter by contact.
     pub async fn search_messages(
         &self,
         query: &str,
         mode: &str,
         limit: usize,
     ) -> Result<Vec<SmsSearchHit>> {
-        let url = format!(
-            "{}/api/messages/search/?q={}&mode={}&limit={}",
-            self.base_url,
-            urlencoding::encode(query),
-            urlencoding::encode(mode),
-            limit
-        );
-
-        let mut request = self.client.get(&url);
-        if let Some(token) = &self.token {
-            request = request.header("Authorization", format!("Bearer {}", token));
-        }
-
-        let response = request.send().await?;
-        if !response.status().is_success() {
-            let status = response.status();
-            let body = response.text().await.unwrap_or_default();
-            return Err(anyhow::anyhow!(
-                "SMS search request failed: {} - {}",
-                status,
-                body
-            ));
-        }
-
-        let data: SmsSearchResponse = response.json().await?;
-        Ok(data.results)
+        self.search_messages_with_contact(query, mode, limit, None).await
     }
 
     /// Same shape as `search_messages` but with optional `contact_id`. The